Mammals
In mammals, pregnancy begins when a fertilized zygote implants in the female's uterus and ends once the fetus leaves the uterus.
Below are average and approximate values ordered by gestation period (note for humans gestational age is counted from the LMP, for other animals the counting method varies, so these figures could be 14 days off):
| Animal | Average gestation period (days) |
|---|---|
| American opossum | 12 - 13 |
| Golden hamster | 15 - 17 |
| House mice | 18 - 20 |
| Rabbits | 33 |
| Foxes | 51 - 63 |
| Cats | 62 |
| Dogs | 65 |
| Coatis | 76-78 |
| Leopards | 94 |
| Lions | 108 |
| Pigs | 115 |
| Beavers | 122 |
| Sheep | 145 |
| Baboons | 187 |
| Moose | 245 |
| Humans | 259–294 |
| Cattle | 283 |
| Horses | 336 |
| Tapirs | 380-400 |
| Giraffes | 420-450 |
| Sperm whales | 480–590 |
| Rhinos | 487 |
| Elephants | 600–660 |
Read more about this topic: Gestation